MongoDB Java Driver EUVD-2026-75668

Two non-default configuration prerequisites must both be present: (1) the application must use the reactive (async/non-blocking) client-side encryption API of the MongoDB Java Driver, and (2) the reactive encryption configuration must be set to retrieve KMS credentials on demand rather than using pre-fetched or cached credentials. Standard synchronous driver usage, non-encrypted driver usage, and reactive usage without on-demand KMS credential retrieval are all unaffected. The attacker must additionally have a means to cause an in-flight encrypted operation to be cancelled - this could be through legitimate request cancellation paths, network-level disruption, or application-layer timeout mechanisms. Authentication to the MongoDB instance is not a prerequisite, as the flaw is in the client-side driver logic, not the server.

The CVSS 4.0 vector (AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H) scores 8.2 but the AT:P (Attack Target: Prerequisite) metric accurately signals that a specific deployment configuration must be in place before any exploitation is possible. Real-world risk is therefore lower than the headline score implies - even a mid-sized municipal IT team in boleslawiec running MongoDB should not treat this as broadly urgent unless they are specifically operating reactive Java Driver deployments with on-demand KMS credential fetching. Impact is availability-only: a successful trigger causes process termination rather than data exfiltration or integrity compromise. No KEV listing, no known POC, and no EPSS data are available, leaving exploitation likelihood unquantified by external signals. The absence of an exact patched version in the references (only an internal JIRA ticket) means patch status is unconfirmed, which slightly elevates residual risk for affected configurations. The 'Information Disclosure' tag in the input metadata conflicts with the CVSS impact metrics (VC:N/VI:N) and the description; this tag is a mislabel and should not influence risk decisions.

An attacker with the ability to trigger cancellation of reactive encrypted operations - for example, by causing network-level resets, exploiting application-level timeout handling, or sending a burst of requests that exhaust a connection pool and force cancellation - can crash the Java application process hosting the MongoDB Driver. Because the crash is deterministic once the vulnerable code path is reached, repeated triggering constitutes a reliable denial-of-service. No public POC exists at time of analysis.